Yeah, call the police. But they probably won't be able to do anything. But just in case they can...
These people, are they just independently wealthy with trust funds or investments to live off? Or do they actually have jobs? Phone the place of employment, ask to speak to the secretary.
Obviously, they're not going to give personal information out like contact details (although if the sparks could give them their phone number, to go towards proving that he'd already been in contact and was legitimate), then the secretary should have emergency contact details and should be able to get in contact with them either by phone or by email.
When I've worked as a secretary, if someone phoned me telling me something like that while my boss was away, I'd have thought my boss was a tit who deserved having his holiday interrupted.
Do they have unusual names? Search for them on Facebook, they're probably online frequently posting pics of themselves quaffing champagne in St Tropez or something. Even if you're not Facebook friends with someone, you can still send them a message.
If it was a week, I'd say it was possibly too much hassle by the time they were tracked down and by the time they received a message, but six weeks not being able to work and earn a living? That's out of order.
It's a shame he's a sparks and not a singer:
But can he not round up some other sparky mates, rig up some outdoor lighting, some of those disco ropes, plugged into their mains with a big message across the front of the house saying: "The owners of this house are selfish, inconsiderate cunts who went on holiday for six weeks leaving my toolkit locked in their house and me unable to support my family." And video it. And publish it on YouTube.
